Messages in this thread Patch in this message | | | Date | Wed, 9 Dec 2009 13:36:45 -0500 | From | Prarit Bhargava <> | Subject | [PATCH]: AMD cache - Fix stale data in shared_cpu_map cpumasks |
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The per_cpu cpuid4_info shared_map can contain stale data when CPUs are added and removed.
The stale data can lead to a NULL pointer derefernce panic on a remove of a CPU that has had siblings previously removed.
This patch resolves the panic by verifying a cpu is actually online before adding it to the shared_cpu_map, only examining cpus that are part of the same lower level cache, and by updating other siblings lowest level cache maps when a cpu is added.
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
diff --git a/arch/x86/kernel/cpu/intel_cacheinfo.c b/arch/x86/kernel/cpu/intel_cacheinfo.c index 0df4c2b..70df1e4 100644 --- a/arch/x86/kernel/cpu/intel_cacheinfo.c +++ b/arch/x86/kernel/cpu/intel_cacheinfo.c @@ -504,18 +504,19 @@ static void __cpuinit cache_shared_cpu_map_setup(unsigned int cpu, int index) { struct _cpuid4_info *this_leaf, *sibling_leaf; unsigned long num_threads_sharing; - int index_msb, i; + int index_msb, i, sibling; struct cpuinfo_x86 *c = &cpu_data(cpu); if ((index == 3) && (c->x86_vendor == X86_VENDOR_AMD)) { - struct cpuinfo_x86 *d; - for_each_online_cpu(i) { + for_each_cpu(i, c->llc_shared_map) { if (!per_cpu(cpuid4_info, i)) continue; - d = &cpu_data(i); this_leaf = CPUID4_INFO_IDX(i, index); - cpumask_copy(to_cpumask(this_leaf->shared_cpu_map), - d->llc_shared_map); + for_each_cpu(sibling, c->llc_shared_map) { + if (!cpu_online(sibling)) + continue; + set_bit(sibling, this_leaf->shared_cpu_map); + } } return; }
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